1. Field of the Invention
The present invention relates to a conveyor assembly and a method of conveying pallets in which the pallets have the ability to couple together in groups of two or more for accepting product of greater length than the individual pallets, and the ability to uncouple for transporting at the terminal ends of the conveyor.
2. Background Art
In order to carry items which are larger than a single pallet, prior art conveyor assembly designs rely upon permanent linking or hinging of carrier or pallets by a variety of types of link bars, which create a permanent grouping of carriers or pallets to carry the large items. This method can be problematic with conveyor designs requiring friction-type terminal transfer of the pallets (i.e., pallet drive mechanisms which require static frictional engagement of surfaces to move the pallets along the chain, and around the sprockets at terminal ends of the chain). As the weight of the pallets increases due to the size of each pallet and the attached tooling or nest fixtures, as well as the hinging of multiple pallets, the subject wear of those designs relying upon friction becomes critical. When wear occurs, the pallets may slip when traveling around the terminal end of the chain drive, which may result in xe2x80x9cslammingxe2x80x9d of pallets traveling from top to bottom, and pallets not having sufficient friction to travel through the terminal end to raise the pallet from the lower level to the upper level of the chain drive mechanism.
Accordingly, it is desirable to provide an improved conveyor system in which large products may be transported along the conveyor system, and in which the weight supported by the friction drive mechanisms is reduced to prevent slipping of pallets around the terminal ends of the chain drives.
It is an object of this invention to overcome the limitations of the prior designs and provide the user of the invention the ability to couple pallets when the product being transported over the conveyor demands so, but allowing the pallets to be uncoupled during other operations of the conveyor. The invention eliminates the concern of linkage binding and allows for more flexibility in design. Such flexibility includes the option of carrying parts which may require single pallets or varying numbers of coupled pallets on demand of the control system.
The carrier or pallets are fitted with sprockets which provide resistance to the chains by means of adjustable clutches and alignment bars which prevent skewing of the carrier or pallets beyond an acceptable tolerance. The sprockets are engaged on the bottom side of the upper multi-strand roller chain and the alignment bars are riding on the top side of the upper multi-strand roller chain.
The multi-strand roller chain is driven by a pair of drive sprockets located at the drive end of the conveyor. At the opposing end of the conveyor similar sprockets act as idler and/or take up sprockets to allow for proper tensioning of the multi-strand roller chain.
Attached to each sprocket is a disc containing rollers of like type and material as the multi-strand roller chain. The disc maintains a matching pitch of the driven and the idler sprockets. The distance between the circumferential pitch diameter of either type of sprocket and the roller disc is such to allow for the carrier or pallet sprocket to become xe2x80x9ctrappedxe2x80x9d between the two during the transfer around the terminal ends of the conveyor.
The alignment bars on either side of the carrier or pallet maintain correct orientation of the carrier or pallet during the engagement of the sprockets in the terminal transitions.
Pallet groups which require coupling to provide a longer pallet xe2x80x9ctrainxe2x80x9d will be fitted with coupling hardware to allow for the automatic coupling of groups of pallets at the loading stop of the conveyor.
The lead pallet in each group of pallets to be coupled has a pair of coupling pivot arms attached to the underside of the pallet top. The pallets following (those intended for coupling) are fitted with a receiving plate which engage with the pivot arm on contact in the load stop station and cause the coupling of the pallets. This coupling may continue for any number of pallets, provided that there is sufficient length at the stop station.
In another embodiment, the pivot arms are spring-loaded.
After coupling up and releasing, the group will travel as one along the length of the conveyor unless stopped by another pallet (creating an accumulation of pallets) or when encountering a stop.
The group may be kept coupled by the use of a keeper rail running the length of the conveyor, which traps the pivot arm large roller and thus prevents the inadvertent release of any single pallet from the train.
When the coupled group of pallets is stopped at the unload station, the group remains coupled together. After being released, the pallets advance. As they do, the pallet pivot arms individually disengage as they roll over a decoupling ramp. After the pallets are decoupled, each will act as an independent pallet at the terminal transfers as well as the empty return of the conveyor.
The above object and other objects, features and advantages of the invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.